The expression of avian sarcoma virus genes at the levels of transcription and translation will be studied. To determine whether transcription of the integrated provirus is initiated at a cellular or viral promoter, the 5' end of the primary nuclear transcript of RSV will be sequenced after labeling with the vaccinia capping enzyme. The possibilities that viral subgenomic mRNAs are transcribed independently and that they have a 5' leader sequence will be investigated. The primary structure of viral RNA isolated from infected cells will be studied by oligonucleotide fingerprinting. Isolated src mRNA will be translated in vitro, and the product(s) will be compared with the possible src gene products previously synthesized from virion RNA. The src protein(s) will be characterized by tryptic peptide mapping, one and two-dimensional gel electrophoresis, immunoprecipitation, and analysis of deletion and temperature-sensitive mutants. The possible function of methylated RNA in the processing of viral mRNA will also be studied by localization of N6-methyladenosine residues in intracellular RNA. In addition, the effect of inhibition of methylation in vivo will be studied.